Optical absorption of metallic Zn nanoparticles in Zn ion implanted sapphire

Zn+ ion implantation (48 keV) was performed at room temperature up to a fluence of 5 × 1017 cm−2 in α-Al2O3 single crystals. X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and optical absorption spectroscopy were utilized to characterize the optical properties, chemical charge states and the microstructure of embedded metallic Zn nanoparticles, respectively. XPS analysis indicated that implanted Zn ions are in the charge state of metallic Zn0. TEM analysis revealed the metallic Zn nanoparticles of 3–10 nm in the as-implanted sample at a fluence of 1 × 1017 cm−2. A selected area electron diffraction (SAD) pattern indicates the random orientation of the Zn nanoparticles. A clear absorption peak appeared gradually in the optical absorption spectra of the as-implanted crystals, due to surface plasma resonance (SPR) of Zn nanoparticles. The wavelength of the absorption peak shifted from 260 nm to 285 nm with the increasing ion fluence, ascribed to the growth of Zn nanoparticles.